The present invention relates to a sheet-like structure with surface protrusions for providing spacing, grip-enhancing, draining elements and the like.
It is known that spacing or draining elements are already commercially available which are provided by means of continuous or perforated sheets, calendered or thermoformed so as to have protrusions or studs on their surface; reticular products with two or more sets of superimposed filaments are also used mostly for drainage purposes.
Both the sheets and the net-like products can be coupled to woven materials, non-woven fabrics or membranes.
Conventional solutions, however, entail several drawbacks: particularly, continuous or perforated sheets shaped by calendering or thermoforming have the drawback that they are fragile and furthermore difficult to compress, owing to the internal flimsiness of the protrusions; it is also necessary to perform significant modifications of the manufacturing equipment if the product is to be modified by changing the number or distribution of the protrusions.
Use of these products as drainage elements is furthermore not particularly favorable, since there is a considerable presence of spacing material because the studs cannot be obtained with a configuration having a very small base; moreover, the studs are subjected, under stress, to a gradual compression which ultimately drastically reduces the draining ability.
Another drawback is furthermore constituted by the fact that the studs molded on the sheet or net must be placed at a relatively significant distance, so that in case of coupling with fabrics said fabric can curve or form arcs in the regions where it is not supported by the studs.
Another problem is furthermore constituted by the fact that calendering of reticular or perforated material can be performed only starting from material with very small openings, in order to avoid compromising the strength of the structure and making production difficult.
It should also be noted that the perforation of a product which has already been calendered to obtain a reticular configuration is unfeasible, both because the method is uneconomical and because the resulting product would be extremely fragile.
The use of products produced with nets having two or more layers of filaments as draining elements is also not particularly advantageous, since the presence of the filaments transversely to the path along which the fluid passes entails a drastic reduction of its draining characteristics.
Moreover, these nets with multiple layers of filaments, when they are not coupled to membranes and/or fabrics, owing to their non-laminar structure, can damage or bite into delicate surfaces, such as sheaths and membranes which are superimposed on it.